ORGANS OF INTERNAL SECRETION 337 



stated that, by means of special methods of staining, droplets 

 of a secretory substance could be detected in the cells of the 

 corpus luteum of the hedgehog. 



Beard ^ independently suggested that the corpus luteum is 

 a contrivance to suppress ovulation during pregnancy, while 

 he supposed it to degenerate before parturition in order to 

 admit of ovulation occurring immediately afterwards. It must 

 be pointed out, however, that in many Mammals, if not in the 

 majority, the breeding season does not recur until after an 

 ancestrous period, which is often of considerable duration, and 

 that it is extremely improbable that ovulation occurs during 

 this period. 



Beard's theory has been adopted by Sandes,^ who investi- 

 gated the corpus luteum of the marsupial cat (Dasyurus vicer- 

 rinus, see p. 149). This author states that in Dasyurus, as in 

 most other Mammals, the corpus luteum disappears towards 

 the end of the lactation period, when the next oestrus is ap- 

 proaching, and the folHcles are beginning to grow in preparation 

 for the ensuing ovulation. He says, further, that as soon as 

 the corpus luteum is formed, the ova in the surrounding follicles, 

 which were up to that time in various stages of active de- 

 velopment, begin to undergo atrophy. This atrophy com- 

 mences in the foUicles in closest proximity to the newly formed 

 corpus luteum, and is continued in the surrounding foUicles in 

 ever-widening circles. Sandes suggests, that this result is 

 brought about by mechanical pressure, or is due to the internal 

 secretion of the corpus luteum, if it has one. Without in any 

 way disputing the accuracy of the facts which Sandes describes, 

 it is difficult to understand what advantage is gained by a 

 mechanism having a not more important object than that of 

 securing the degeneration of the surplus ova within the ovary 

 instead of externally to it, and it is not easy to see how, ac- 

 cording to the usually accepted doctrines of utility and natural 

 selection, an organ having such a purposeless function could 

 ever have been developed at all. 



Gustav Born was the first to suggest that the function of 



' Beard, The Span of Gestation and the Cause of Birth, Jena, 1897. 

 ' Sandes, " The Corpus Luteum of Dasyurus viverrinus," Proc. lAnnean 

 Soc, New South Wales, vol. xxviii., 1903. 



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